Method of producing annealed polyvinyl alcohol contact lens
AssigneeCiba-Geigy Corporation
InventorPing I. Lee
Life of this patent
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Abstract
Optically clear soft contact lenses of aqueous swollen solid polyvinyl alcohol having a weight average molecular weight of at least 6,000, having been annealed under crystallinity promoting conditions to effectively increase the elastic modulus of the swollen lenses, and optionally subsequently crosslinked, and methods of preparation and the use thereof are disclosed. The lenses are characterized by their relatively high oxygen transmissibility, sufficient to meet the needs of the human cornea, high optical clarity, improved hot water resistance and superior mechanical properties.
Claims32
In a method of providing corrected vision in patients in need of the same comprising wearing a soft contact lens on the surface of the cornea, the improvement wherein the soft contact lens is an optically clear soft contact lens of swollens solid polyvinyl alcohol having a weight average molecular weight of at least about 6,000, which has been annealed, without prior crosslinking, under crystallinity promoting conditions, to substantially increase the crystallinity thereof, and swollen in a swelling solvent, the resultant annealed, swollen lens possessing an oxygen transmissibility capability in an aqueous environment in excess of that necessary to meet the needs of the human cornea.
A process for preparing an optically clear soft contact lens of swollen solid polyvinyl alcohol having a weight average molecular weight of at least about 6,000, which has been annealed, without prior crosslinking, under crystallinity promoting conditions, to substantially increase the crystallinity thereof, and swollen in a swelling solvent, the resultant annealed, swollen lens possessing an oxygen transmissibility capability in an aqueous environment in excess of that necessary to meet the needs of the human cornea comprising:
- (a) forming a lens blank from a substantially non-crosslinked polyvinyl alcohol resin having a weight average molecular weight of at least 6,000;
- (b) annealing said lens blank under crystallinity promoting conditions to effectively increase the elastic modulus of the subsequently swollen contact lens, such that the resulting annealed polyvinyl alcohol blank has a degree of crystallinity between about 0.195 and 0.70 based on the weight fraction of crystalline material present in the polyvinyl alcohol polymer;
- (c) removing selected portions of said annealed blank until the remainder of the annealed blank constitutes a replica of said contact lens on a reduced scale;
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- (d) swelling said annealed replica in an aqueous or nonaqueous swelling solvent, to obtain said substantially shape-retaining swollen contact lens, wherein said lens in its swollen equilibrium state with ocular tear fluid, possesses sufficient oxygen transmissibility to meet the needs of the human cornea.
A process for preparing an optically clear soft contact lens of swollen solid polyvinyl alcohol having a weight average molecular weight of at least about 6,000, which has been annealed, without prior crosslinking, under crystallinity promoting conditions, to substantially increase the crystallinity thereof, and swollen in a swelling solvent, the resultant annealed, swollen lens posessing an oxygen transmissibility capability in an aqueous environment in excess of that necessary to meet the needs of the human cornea comprising:
- (a) forming a lens blank from a substantially non-crosslinked polyvinyl alcohol resin having a weight average molecular weight of at least 6,000;
- (b) annealing said lens blank under crystallinity promoting conditions to effectively increase the elastic modulus of the subsequently swollen contact lens, such that the resulting annealed polyvinyl alcohol blank has a degree of crystallinity between about 0.195 and 0.70 based on the weight fraction of crystalline material present in the polyvinyl alcohol polymer;
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- (c) swelling said annealed replica in an aqueous or nonaqueous swelling solvent, to obtain said substantially shape-retaining swollen contact lens, wherein said lens in its swollen equilibrium state with ocular tear fluid, possesses sufficient oxygen transmissibility to meet the needs of the human cornea.
Dependencies are inferred from the claim text.